Letter: Reston Traffic: From Difficult to Impossible

Monday evening the county’s Department of Transportation (DOT) staff presented the Master Plan Task Force its latest analysis for traffic in Reston in 2030. The presentation was based on the task force’s current planning proposal for Reston near the Dulles Corridor, called “Scenario G.”

This scenario was necessitated by the abysmal failure of an earlier office-focused development proposal, “Scenario E,” to handle traffic at Reston’s intersections.

The traffic impact analysis, using sophisticated traffic engineering modeling, shows that we can routinely expect morning and evening “peak period” traffic at intersections along Reston’s major streets near the corridor to earn a grade of “F.” Amazingly, that’s actually a modest improvement (8 percent) over the preceding scenario’s grade that can only be

described as “F-.”

Warning: This letter is a little long and traffic wonkish.

And, yes, for all practical purposes, that grade is very much like the one you, I, and our children experienced going through school. An “F” means that an intersection fails to handle its traffic; traffic is gridlocked. It is a “level of service” (LOS) metric that is part of a national urban transportation standard most recently updated in 2010.

There are basically two dimensions to the metric: whether the

intersection is at or over capacity and the duration of traffic delays at the intersection. An “F” grade is given to intersections that are either over capacity or where average traffic delays exceed 80 seconds.

It means that:

Most cycles fail to clear the queue… A (volume-to-capacity) ratio of 1.0 or more indicates that cycle capacity is fully utilized and represents failure from a capacity perspective (just as delay in excess of 80 seconds per vehicle represents failure from a delay perspective).

And DOT’s analysis shows that Reston’s seven “gateway” intersections along the Dulles Corridor under Scenario G would average well over two minutes each during peak periods. For example, the intersection of Wiehle Avenue and Sunset Hills would have an evening “peak period” forecast delay of 253 seconds. Yes, that is four minutes and 13 seconds to get through that intersection—on an average day. Today that

intersection has an LOS “E” (55-80 seconds average delay) in the evening rush period, one-third to one-fifth what we can expect in 2030.

The four “gateway” intersections on Reston Parkway and Wiehle Drive at Sunset Hills and Sunrise Valley Drive have an average peak evening rush period delay of about 152 seconds in Scenario G. With the exception of Wiehle/Sunrise Valley, all these intersections are well into the LOS “F” range; Wiehle/Sunrise Valley earns an LOS “D”. Today, only the Reston Parkway/Sunrise Valley intersection among these four intersections warrants and LOS “F” in either the morning or evening peak periods.

Can you imagine what traffic will be like with a little rain, sleet,

snow or even a minor accident along the way?

If you happen to be traveling from north to south (or vice versa) in Reston (say, taking your son or daughter to soccer practice on the other side of town), you can count on going through several such intersections, particularly at Sunset Hills and Sunrise Valley along Reston Parkway and Wiehle. Though delays at these four intersections average more than five minutes during the peak traffic periods.

These delays do not count what DOT calls “spill back,” the queuing of vehicles so badly on a street that it blocks the preceding intersection. DOT will study this phenomenon before it submits its required report to the Virginia DOT. With three and four minute delays at these core intersections, “spill back” will be a virtual pervasive certainty during peak periods. Indeed, it is part of the definition of an LOS “F.”

Traffic will move from gridlocked to a complete standstill.

Maybe more importantly, these adverse outcomes assume an aggressive county campaign of investment in roadways, bus transit, bicycling and pedestrian access, and traffic demand management (TDM) well beyond the current county plan. The big budget items include new connections over the Toll Road for Soapstone Drive, Town Center Parkway, and South Lakes

Drive. It would also include a grade-separated crossing (an

interchange) at the corner of Fairfax County Parkway and Sunrise Valley Drive. It also includes a grid of streets around the stations, a few street extensions (such as Pinecrest to Sunrise Valley Drive), and lane additions at gateway intersections. These roadway improvements alone would add well over a half-billion 2013 dollars to the county’s

transportation spending budget. And, of course, we haven’t begun to discuss who would pay for those improvements.

These disastrous traffic results are set against a current county-wide urban transportation standard for Reston and other transit areas that now stands with an LOS target of “D” for its roadways—which is about as high as urban area intersections ought to be. The Tysons transportation

plan calls for achieving a LOS target of “E. Now Supervisor Hudgins has asked the county staff to look at establishing a traffic standard for Reston “similar to Tysons,” which likely means LOS “E.” Even with LOS “E,” which the handbook characterizes as “when the volume-to-capacity ratio is high, progression is unfavorable, and the cycle length is long. Individual cycle failures are frequent,” there is little prospect of Reston’s gateway intersections ever achieving this standard no matter how much money and effort is put into it. It would

be a hollow, cynical goal unless the county is willing to constrain station area development to permit it to occur—an outcome it has not yet supported anywhere, including Tysons.

The one flicker of hope in all this forecasting is that DOT’s tested level of traffic impact may be too high. As it normally does, DOT analyzed the traffic impact based on development reaching 83.3 percent of the proposed Scenario G capacity in the station areas and a county version of MWCOG’s forecast for jobs and household growth beyond those areas.

These forecasts are likely too optimistic for the 2030 timeframe.

Indeed, MWCOG is reducing its growth estimates for 2030 as it moves from Round 8.0 (the base for this traffic analysis) to 8.1 and now 8.2 of its Washington area forecasts. Moreover, as we are all aware, sequestration and general federal austerity are likely to slow regional and local growth for at least a decade absent some unforeseeable circumstance.

Nonetheless, at some point in time—maybe earlier, maybe later than 2030—the number of jobs and residents in Reston will reach the levels DOT tested with the traffic-stopping results they forecast.

The result is that, even if Reston is lucky enough to obtain all the funding, build all the critical roadway improvements, step up its transit program to meet an urban requirement, and complete the many pedestrian and bicycling pathways and lanes required, traffic across this community during peak periods will move from the difficult situation we face today to an impossible condition in the future. In the almost certain absence of at least some of these improvements, traffic conditions in Reston will be worse than forecast.

Is this “F” peak period intersection congestion condition good enough for Reston’s major Dulles Corridor thoroughfares? Do we need to reduce planned growth to enable greater mobility within Reston? What else can we do to prevent traffic failure?

It’s your community; you decide. Once you have decided, let Supervisor Hudgins and Reston Task Force Chairman Patty Nicoson know what you think. Please add Heidi Merkel, the leader of the planning staff effort supporting the task force, and me, RCA’s representative to the task force to those communications, to your communications so we can